Double Sintered Thermally Stable Polycrystalline Diamond Cutting Elements

ABSTRACT

Embodiments of the invention include a polycrystalline diamond compact comprising a plurality of double-sintered polycrystalline diamond segments. The polycrystalline diamond segments are configured to remain thermally stable at a first temperature. The polycrystalline diamond segments are positioned upon and bonded to a transition layer of single-sintered polycrystalline diamond that is configured to remain thermally stable at a second temperature lower than the first temperature. The transition layer is positioned upon and bonded to a substrate. Embodiments of the invention have improved thermally stability, resulting in fewer defects during manufacturing and improved longevity in use.

PRIORITY CLAIM

This application claims the benefit of and priority from U.S.Provisional Patent Application No. 61/164,770 filed on Mar. 30, 2009,which is incorporated herein in its entirety for all purposes by thisreference.

FIELD

Embodiments of the present invention relate generally to the field ofearth boring tools and in particular relates to polycrystalline diamondcutting elements used on drill bits for earth boring.

BACKGROUND

Specialized drill bits are used to drill well-bores, boreholes, or wellsin the earth for a variety of purposes, including water wells; oil andgas wells; injection wells; geothermal wells; monitoring wells, mining;and, other similar operations. These drill bits come in two commontypes, roller cone drill bits and fixed cutter drill bits.

Wells and other holes in the earth are drilled by attaching orconnecting a drill bit to some means of turning the drill bit. In someinstances, such as in some mining applications, the drill bit isattached directly to a shaft that is turned by a motor, engine, drive,or other means of providing torque to rotate the drill bit.

In other applications, such as oil and gas drilling, the well may beseveral thousand feet or more in total depth. In these circumstances,the drill bit is connected to the surface of the earth by what isreferred to as a drill string and a motor or drive that rotates thedrill bit. The drill string typically comprises several elements thatmay include a special down-hole motor configured to provide additionalor, if a surfaces motor or drive is not provided, the only means ofturning the drill bit. Special logging and directional tools to measurevarious physical characteristics of the geological formation beingdrilled and to measure the location of the drill bit and drill stringmay be employed. Additional drill collars, heavy, thick-walled pipe,typically provide weight that is used to push the drill bit into theformation. Finally, drill pipe connects these elements, the drill bit,down-hole motor, logging tools, and drill collars, to the surface wherea motor or drive mechanism turns the entire drill string and,consequently, the drill bit, to engage the drill bit with the geologicalformation to drill the well-bore deeper.

As a well is drilled, fluid, typically a water or oil based fluidreferred to as drilling mud is pumped down the drill string through thedrill pipe and any other elements present and through the drill bit.Other types of drilling fluids are sometimes used, including air,nitrogen, foams, mists, and other combinations of gases, but forpurposes of this application drilling fluid and/or drilling mud refersto any type of drilling fluid, including gases. In other words, drillbits typically have a fluid channel within the drill bit to allow thedrilling mud to pass through the bit and out one or more jets, ports, ornozzles. The purpose of the drilling fluid is to cool and lubricate thedrill bit, stabilize the well-bore from collapsing or allowing fluidspresent in the geological formation from entering the well-bore, and tocarry fragments or cuttings removed by the drill bit up the annulus andout of the well-bore. While the drilling fluid typically is pumpedthrough the inner annulus of the drill string and out of the drill bit,drilling fluid can be reverse-circulated. That is, the drilling fluidcan be pumped down the annulus (the space between the exterior of thedrill pipe and the wall of the well-bore) of the well-bore, across theface of the drill bit, and into the inner fluid channels of the drillbit through the jets or nozzles and up into the drill string.

Roller cone drill bits were the most common type of bit usedhistorically and featured two or more rotating cones with cuttingelements, or teeth, on each cone. Roller cone drill bits typically havea relatively short period of use as the cutting elements and supportbearings for the roller cones typically wear out and fail after only 50hours of drilling use.

Because of the relatively short life of roller cone bits, fixed cutterdrill bits that employ very durable polycrystalline diamond (PCD)compact cutters, tungsten carbide cutters, natural or synthetic diamond,other hard materials, or combinations thereof, have been developed.These bits are referred to as fixed cutter bits because they employcutting elements positioned on one or more fixed blades in selectedlocations or randomly distributed. Unlike roller cone bits that havecutting elements on a cone that rotates, in addition to the rotationimparted by a motor or drive, fixed cutter bits do not rotateindependently of the rotation imparted by the motor or drive mechanism.Through varying improvements, the durability of fixed cutter bits hasimproved sufficiently to make them cost effective in terms of time savedduring the drilling process when compared to the higher, up-front costto manufacture the fixed cutter bits.

Typically, a diamond cutter for use in a drill bit having a geometricsize and shape normally characterized by unleached diamond cuttingelements fabricated by assembling a plurality of polycrystalline diamondcompact cutting elements in an array in a cutting slug that supports thecutting element. A challenge occurs, however, in bonding the PCD cuttingelements to the cutting slug because the cutting slug—typically acemented carbide substrate—has a different material than the PCD cuttingelements and, therefore, has different material properties, such as adifferent rate of thermal expansion than the PCD cutting element. Thedifferences in material properties can cause thermal stresses that leadthe PCD cutting element to crack, delaminate, or otherwise becomeweakened and/or damaged at the interface between the cutting slug andthe PCD cutting element.

Thus, there exists a need for a PCD cutting element that is, at least inpart, has improved thermal compatibility with the underlying cuttingslug.

Further, there is a need for a PCD cutting element that has improvedbonding to a cutting slug as compared to the prior art.

In addition, there is a need for a PCD manufacturing process thatimproves the yield of usable PCD cutting elements coupled to cuttingslugs that reduces the probability that the PCD cutting elements breakand/or crack during a double sintering process.

SUMMARY

Various features and embodiments of the invention disclosed hereinprovide robust and durable PCD cutting elements coupled to a cuttingslug. In addition, methods of coupling a PCD cutting elements to acutting slug are also disclosed.

Embodiments of the invention include a first layer comprising at leastone polycrystalline diamond segment positioned upon a second layer ortransition layer. In those embodiments that include a plurality of PCDsegments, a first PCD segment is positioned proximate a second PCDsegment and separated therefrom by an interfacial boundary. Theinterfacial boundary optionally is non-planar relative to the firstand/or the second PCD segment. Optionally, the interfacial boundaryincludes an abrasive material. Optionally, the interfacial boundary iscontiguous with and formed of the same material as the second layer. Insome embodiments, the first layer remains thermally stable at a highertemperature than the temperature below which the second table remainsthermally stable. In some embodiments, the second layer is coupled to asubstrate or cutting slug.

Embodiments of the PCD segments include those that have been processedto provide a granular structure comprising interstices with a reducednumber of metallic catalysts. Other embodiments of the PCD segmentsinclude those that have been processed to provide a granular structurethat include interstices infiltrated with a material that remainsthermally stable at a higher temperature than the temperature belowwhich the metallic catalysts remain thermally stable. Other embodimentsof the granular structure of the PCD segments comprise interstices thatinclude one or more non-metallic catalysts. Yet other embodiments of thegranular structure of the PCD segments comprise substantially fullydense diamond, i.e., a granular structure being substantially free ofvoids and/or interstices with or without other materials within anyremaining interstices.

Other embodiments of the invention include a body of abrasive materialcoupled to a substrate. The body includes a substantially pointed orconical shaped cutting surface. The body optionally includes one or morePCD segments coupled to and exposed in the conical cutting surface.

A method of forming a PCD cutting elements coupled to a cutting slugincludes providing a canister or other container configured to receive aplurality of thermally stable pre-sintered polycrystalline diamondsegments. The canister is filled with grains of polycrystalline diamondand, optionally, a catalytic material. The polycrystalline diamondsegments are positioned upon the grains of polycrystalline diamond suchthat an interfacial boundary is formed from the grains ofpolycrystalline diamond to separate each of the plurality ofpolycrystalline diamond segments. A press than applies a temperature anda pressure to the container to sinter the grains of polycrystallinediamond and bond the polycrystalline diamond segments to the sinteredgrains of polycrystalline diamond.

As used herein, “at least one,” “one or more,” and “and/or” areopen-ended expressions that are both conjunctive and disjunctive inoperation. For example, each of the expressions “at least one of A, Band C,” “at least one of A, B, or C,” “one or more of A, B, and C,” “oneor more of A, B, or C” and “A, B, and/or C” means A alone, B alone, Calone, A and B together, A and C together, B and C together, or A, B andC together.

Various embodiments of the present inventions are set forth in theattached figures and in the Detailed Description as provided herein andas embodied by the claims. It should be understood, however, that thisSummary does not contain all of the aspects and embodiments of the oneor more present inventions, is not meant to be limiting or restrictivein any manner, and that the invention(s) as disclosed herein is/are andwill be understood by those of ordinary skill in the art to encompassobvious improvements and modifications thereto.

Additional advantages of the present invention will become readilyapparent from the following discussion, particularly when taken togetherwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

To further clarify the above and other advantages and features of theone or more present inventions, reference to specific embodimentsthereof are illustrated in the appended drawings. The drawings depictonly exemplary embodiments and are therefore not to be consideredlimiting. One or more embodiments will be described and explained withadditional specificity and detail through the use of the accompanyingdrawings in which:

FIG. 1 is an isometric view of an embodiment of a PCD compact cuttingelement;

FIG. 2 is a microscopic level view of an embodiment of a granularstructure of a PCD segment;

FIG. 3 is a microscopic level view of another embodiment of a granularstructure of a PCD segment;

FIG. 4 is an isometric view of an embodiment of a metallic carbide discfor use in embodiments of methods of making a PCD segment;

FIG. 5 is an isometric view of another embodiment of a metallic carbidedisc for use in embodiments of methods of making a PCD segment;

FIG. 6A is a cross-sectional view of an embodiment of a canister for usein embodiments of methods of making a PCD segment;

FIG. 6B is a cross-sectional view of an embodiment of a canister for usein embodiments of methods of making a PCD compact;

FIG. 7 is an orthogonal view of an embodiment of a PCD cutting element;

FIG. 8 is an orthogonal diagram of another embodiment of a PCD cuttingelement;

FIG. 9 is an orthogonal diagram of another embodiment of a PCD cuttingelement;

FIG. 10 is an orthogonal diagram of another embodiment of a PCD cuttingelement;

FIG. 11 is an orthogonal diagram of another embodiment of a PCD cuttingelement;

FIG. 12 is an orthogonal diagram of another embodiment of a PCD cuttingelement;

FIG. 13 is an orthogonal diagram of another embodiment of a PCD cuttingelement;

FIG. 14 is an orthogonal diagram of another embodiment of a PCD cuttingelement;

FIG. 15 is a cross-sectional view of an embodiment of a PCD cuttingelement;

FIG. 16 is a cross-sectional view of another embodiment of a PCD cuttingelement;

FIG. 17 is a cross-sectional view of another embodiment of a PCD cuttingelement;

FIG. 18 is a cross-sectional view of another embodiment of a PCD cuttingelement;

FIG. 19 is a cross-sectional view of another embodiment of a PCD cuttingelement;

FIG. 20 is a cross-sectional view of another embodiment of a PCD cuttingelement;

FIG. 21 is an isometric view of an embodiment of a rotary drag bit thatincludes an embodiment of a PCD compact cutting element in a close-upview;

FIG. 22 is an isometric view of an embodiment of a PCD compact cuttingelement that includes a transition layer with a conical surface;

FIG. 23 is an isometric view of another embodiment of a rotary drag bitthat includes an embodiment of a PCD compact cutting element thatincludes a conical surface in a close-up view;

FIG. 24 is an orthogonal view of another embodiment of a PCD cuttingelement;

FIG. 25 is an orthogonal view of another embodiment of a PCD cuttingelement; and,

FIG. 26 is an orthogonal view of another embodiment of a PCD cuttingelement;

The drawings are not necessarily to scale.

DETAILED DESCRIPTION

FIG. 1 shows an isometric view of an embodiment of a polycrystallinediamond (PCD) compact 101. The PCD compact 101 includes a first table orlayer 105 formed of a plurality of PCD segments 110 that, optionally,are sintered and/or preformed, as will be described in further detailbelow. The PCD segments 110 optionally are leached diamond, naturaldiamond, synthetic diamond, highly pressurized diamond, calciumcarbonate sintered diamond, combinations thereof, and similar materialsand for purposes of the claims a PCD segment and/or polycrystallinediamond encompasses all these materials and those that fall within thescope of this disclosure. In addition, the PCD segments 110 optionallyare thermally stable as will be described in further detail below. Inthe embodiment of the PCD compact 101 illustrated in FIG. 1, the firstlayer 105 has a diameter of 130. Of course, one of skill in the art willappreciate that the first layer 105 can optionally have differentdimensions and different shapes, including ovoid, half-circle, square,and other such shapes, and that all of these embodiments fall within thescope of the disclosure.

The plurality of PCD segments 110 are separated by an interfacialboundary 150 between each of the plurality of PCD segments 110.Optionally, the interfacial boundaries 150 comprises an abrasivematerial selected from a group that includes, but is not limited to,tungsten carbide, cubic boron nitride, thermally stable polycrystallinediamond, polycrystalline diamond, and the like. The interfacialboundaries 150 optionally are non-linear and/or non-planar relative toadjacent PCD segments 110. Optionally, the non-linear and/or non-planarquality of the interfacial boundary 150 creates an interlockingfeature—best seen as interlocking feature 760 in FIG. 7 and interlockingfeature 960 in FIG. 9—between the diamond segments 110, thereby reducingthe likelihood that adjacent PCD segments 110 will move relative to eachother and, therefore, reducing the likelihood of a PCD segment 110 beingtorn and/or damaged and/or removed undesirably from the PCD compact 101during use.

The PCD compact 101 also includes a second table or layer 115, alsoreferred to as a transition layer 115. The PCD segments 110 arepositioned upon and bonded to the second layer 115. The second layer 115optionally comprises an abrasive material selected from a group thatincludes, but is not limited to, tungsten carbide, cubic boron nitride,thermally stable polycrystalline diamond, polycrystalline diamond, andthe like. The embodiment of the PCD compact 101 illustrates a secondlayer 115 that includes sintered PCD grains 120 that is optionallyinterspersed with a metallic catalyst. Optionally, the second layer 115is contiguous with and comprises the same material as the interfacialboundary 150. In the embodiment of the PCD compact 101 illustrated inFIG. 1, the second layer 115 has a diameter of 135 that is the same,within manufacturing tolerances, as the diameter 130 of the first layer105. Of course, one of skill in the art will appreciate that the secondlayer 115 can optionally have different dimensions and different shapes,including ovoid, half-circle, square, and other such shapes, includingdimensions and shapes different from the first layer 105, and that allof these embodiments fall within the scope of the disclosure.

The second table 115 is bonded to a substrate 125 made from, forexample, a metallic material. For example, the substrate 125 can be madefrom a metallic material selected from the group that includes, but isnot limited to, tungsten carbide, titanium carbide, tungsten molybdenumcarbide, tantalum carbide, combinations thereof, and other similarmaterials. In the embodiment of the PCD compact 101 illustrated in FIG.1, the substrate 125 has a diameter of 140 that is the same, withinmanufacturing tolerances, as the diameter 130 of the first layer 105 andthe diameter 135 of the second layer 115. Of course, one of skill in theart will appreciate that the substrate 125 can optionally have differentdimensions and different shapes, including ovoid, half-circle, square,and other such shapes, including dimensions and shapes different fromthe first layer 105 and/or the second layer 115, and that all of theseembodiments fall within the scope of the disclosure.

As noted, the PCD segments 110 typically are formed by sinteringpowdered diamond, and, optionally, various catalysts, typically metallicpowders mixed with the diamond powder. The catalysts, typically metallicmaterials, such as cobalt and other similar metallic materials, act as acatalyst to reduce the temperature and/or the pressure at which thesintering process occurs and/or speeds the reaction by which the diamondgrains and any other materials crystallize and form a granularstructure. The diamond powder and any catalysts and/or other materialsare placed in a canister or form that is compressed under a pressure anda temperature sufficient to sinter and crystallize the diamond powderand any other materials into a solid PCD segment.

Referring to FIG. 3, a sintered PCD granular structure 300 comprisespolycrystalline diamond grains or crystals 301 and a catalyzing material310 dispersed between the polycrystalline diamond grains or crystals301. Optionally, the catalyzing material 310 is selected from a group ofmetallic materials, including, but not limited to, cobalt, nickel, iron,ruthenium, rhodium, palladium, platinum, chromium, manganese, tantalum,osmium, iridium, and combinations thereof.

Cobalt and other catalysts, however, typically result in a PCD granularstructure that typically suffers from thermal degradation attemperatures (typically around from about 650 degrees Celsius to about700 degrees Celsius) that the PCD granular structure can be exposed toduring normal use. That is, the PCD granular structure exhibitsincreased tendencies to fail, crack, chip, delaminate, or otherwise wearmore quickly during use at normal operating temperatures, leading topremature wear and reduced life.

To address the side-effect the catalysts 310 have on the thermalstability of the PCD granular structure 300, the PCD segments (such assegments 110 in FIG. 1) are processed after they have been sintered toreduce the amount of catalyst 310 present in the PCD granular structure300 or remove the catalyst 310, either from the entire PCD segment or atleast to a depth at which the PCD segment is heated through the transferof heat generated during use less than the temperature at which the PCDgranular structure begins to exhibit decreased thermal stability.Typically, the catalysts are removed via leaching and/or acid etchingwith acids that react with the catalysts and/or other known methods,leaving a PCD segment that is said to be thermally stable, typicallyreferred to as thermally stable polycrystalline (TSP).

Illustrated in FIG. 2 is an idealized microscopic level view of asintered PCD granular structure 200 that has been processed to removethe catalyst (e.g., catalyst 220 in FIG. 3), thereby leaving voids 220and PCD grains 201, as discussed above. That is, the thermally stablePCD segments 110 of FIG. 1 optionally have been processed in such a wayto improve the thermal stability of the PCD segments 110 relative to PCDsegments that have not undergone such processing. Improved thermalstability means that the diamond segments remain stable, e.g., do notexhibit increased tendencies to fail, crack, chip, delaminate, orotherwise wear more quickly during use at higher temperatures than thesefailure modes would otherwise manifest themselves.

The PCD grains 201 typically are submicron in size, providingdimensional context for the FIGS. 2 and 3, typically from about 1 micronto about 50 microns and, more preferably, from about 5 microns to about35 microns and, more preferably still, from about 7 microns to about 25microns. In some embodiments, the PCD granular structure is processed toprovide PCD grains 201 large enough such that the PCD grains 201 do noteasily oxidize and burn up when subjected to the heat caused by frictionduring use.

Optionally, the PCD granular structure 200 is then subjected toadditional processing, such as another sintering process (i.e., doublesintering) to cause the PCD grains 201 to grow and expand into theinterstices or voids 220, leaving PCD granular structure that issubstantially diamond dense. That is, the PCD granular structure 200comprises at least 90% PCD grains 201.

In other embodiments, the PCD granular structure 200 is sintered whilein contact with non-catalytic materials, i.e., those materials thattypically do not catalyze or cause the PCD granular structure to changecrystal structure (e.g., from diamond to graphite) and/or lower thetemperature at which the PCD granular structure 200 and PCD grains 201begin to become thermally unstable. For example, a non-metallic catalyst210 that is thermally stable, e.g., one having a coefficient of thermalexpansion similar to that of the PCD grains 201 can be placed in contactwith the PCD granular structure 201 during the sintering process,thereby causing the non-metallic catalyst 210 to infiltrate and/or growwithin one or more of the interstices or voids 220. The non-metalliccatalyst 210 can be selected from a group that includes, but is notlimited to, silicon, silicon carbide, boron, carbonates, hydroxide,hydride, hydrate, phosphorus-oxide, phosphoric acid, carbonate,lanthanide, actinide, phosphate hydrate, hydrogen phosphate, phosphoruscarbonate, combinations thereof, and other similar materials.

In yet other embodiments, the PCD granular structure 200 is sinteredwith one or more thermally stable materials 215, including, but notlimited to, cobalt silicide, titanium, niobium, molybdenum, tungsten,tantalum, combinations thereof, and other similar materials. A benefitof these thermally stable materials 215 is that they tend to act to makethe PCD granular structure 200 less brittle under impact loads.

Prior art PCD compacts typically had a PCD segment bonded directly to asubstrate. This arrangement caused difficulties during manufacturing anduse because, among other problems, the coefficient of thermal expansiondiffered, sometimes greatly, between the substrate and the PCD segment.During manufacturing, in which the PCD segment was to be bonded to thesubstrate, the different rates of thermal expansion often resulted inPCD segments that cracked due to the thermal stresses created at theinterface of the substrate and the PCD segment as the substrate and PCDsegment expanded and contracted at different rates while heating andcooling. Similar results occurred during use in which the PCD segmentwould be subjected to direct heating caused by friction, whereas thesubstrate is heated primarily through heat transferred by conductionthrough the PCD segment and to the substrate.

A benefit of the second layer or transition layer 115 is that it solvesthe previously unresolved problem of bonding a PCD segment to asubstrate that has a different coefficient of thermal expansion. Thatis, embodiments of PCD compacts of the invention have improved thermalstability, improved bonding of the PCD segments to a substrate, improvedreliability, and other benefits as described herein and one having skillin the art will understand by reading the disclosure.

Embodiments of methods of making first the PCD segments 110 are firstdiscussed. As noted above, PCD segments 110 are formed by sinteringdiamond powder or other similar material and, optionally, a catalyst.Illustrated in FIGS. 4 and 5 are discs 405, 410, that are provided. Thediscs 405, 410 optionally formed of a metallic carbide, such as thosematerials discussed above. The discs 405 and 410 are used to shape thePCD segments 110. The discs 405, 410 include one or more areas 415 inwhich the PCD segments 110 are formed, the areas 415 being separated byone or more ribs 420 on a front surface 409 of the discs 405, 410. Theribs 420 may be straight, non-liner, curvilinear, non-planar,combinations thereof, and the like. (It should be noted that shape andlocation of the ribs 420 is a mirror of the shape and location of theinterfacial boundary 150 of the PCD compact 101 discussed above. Thus,the ribs 420 can optionally be of any shape and any dimensioncontemplated for the interfacial boundaries.) In addition, the ribs 420separate the PCD segments 110 from coming into contact with each otherduring the manufacturing process.

Embodiments of the method making PCD include providing a canister or can601 as seen in FIG. 6A. At least one disc or a first disc 405 is placedwithin the canister 601 and each area 415 of the disc 405 is filledwith, for example, diamond powder 650 (and any catalysts and othermaterials, which are considered present in the discussion of the diamondpowder 650), as discussed above, that will be sintered to form the PCDsegment 110, as discussed above. In those instances in which a pluralityof discs 405 are placed into the canister 601 so as to form a pluralityof PCD segments 110, optionally another disc 630 separates each disc 405from the diamond powder 650 proximate to a back surface 407 of each disc405. The disc 630 optionally is made of niobium and/or similar suchmaterials, which prevents, at least to some degree, the flow of diamondpowder 650 and the growth of crystallized diamond grains into the backsurface 407 of the disc 405 during sintering. The number of discs 405positioned in the canister 601 and, consequently, the number of PCDsegments 110 produced, is a function, in part, of the thickness 655 ofthe layer of diamond powder 650 and the thickness 408 of the discs 405.Of course, the thickness 655 of the diamond powder 650 and the thickness408 of the disc 405 optionally can be varied in the same canister 601,thus producing PCD segments of different dimensions in one manufacturingbatch. Further, as one having skill in the art will appreciate, thequantity of PCD segments 110 produced is a function, in part, on theconfiguration and number of ribs 420 on each disc 405. Further,different discs 405 with different configurations of ribs 420 can beused in a given canister 601, thus further affecting the yield of PCDsegments 110.

Prior to placing the lid 660 on the canister 601 and sealing thecanister 601, the diamond powder 650 may be tamped down or compactedwith an applied pressure low enough to avoid breakage of any of thediscs 405 and 630. Optionally, the canister 650 is heated to reduce oreliminate some or all of any impurities present in the diamond powder650 and elsewhere in the canister 601 before sealing the canister 601.Typically, the lid 660 is sealed to the canister 601 through welding,such as laser welding and other known methods. In some embodiments ofthe present invention, the canister is sealed using a process describedin U.S. Pat. No. 7,575,425 to Hall et al., which is herein incorporatedby reference for all that it contains.

After the canister 601 is sealed, it is placed within a salt form (notshown). One or more salt forms are then stacked and placed on an anvilof a high-temperature, high-pressure press (not shown). The pressapplies a pressure and a temperature sufficiently high to cause thediamond powder 650 (and any catalysts and other materials) to sinter.During the sintering process, the diamond powder 650 typically reducesin volume as it becomes solid.

Once the sintering process is complete and the canister 601 is removedfrom both the press and the salt form, the diamond powder 650 will havebecome the sintered PCD segments 110. An advantage of the ribs 420 ofthe discs 405 is that the separate PCD segments 110 are easily separablefrom the discs 420, thus eliminating a step of cutting the PCD segments110 out a solid cylinder of polycrystalline diamond with an electrondischarge machining (EDM), a process that typically is time consumingand expensive. The separated PCD segments 110 are now ready for anypost-sintering treatment such as leaching and/or acid baths, and othersuch treatments to improve the thermal stability of the PCD segments 110as discussed above.

Embodiments of the method further include forming PCD compacts, such asthose illustrated in FIG. 1, to combine PCD segments 110 with anunsintered abrasive powder or material that will form the second ortransition layer 115 and a substrate 125. One or more PCD segments 2610are placed in a canister 2601, similar to the canister 601, asillustrated in FIG. 6B. Unsintered abrasive material 2620, such asdiamond powder, by way of example, is placed in the canister inbetween—at the interfacial boundary 2650—and on top of the PCD segments2610 that typically have been processed to improve the thermal stabilityof the PCD segments 2610, as discussed above. As noted above, theunsintered abrasive material optionally includes metallic catalystsand/or non-metallic catalysts and/or other thermally stable materials asdiscussed above.

The substrate 2625 is placed on top of the unsintered abrasive material2620. Prior to placing the lid 2660 on the canister 2601 and sealing thecanister 2601, the unsintered abrasive material 2620 may be tamped downor compacted with an applied pressure low enough to avoid breakage ofany of the PCD segments 2610. Optionally, the canister 2601 is heated toreduce or eliminate some or all of any impurities present in theunsintered abrasive material 2620 and elsewhere in the canister 2601before sealing the canister 2601. Typically, the lid 2660 is sealed tothe canister 2601 through welding, such as laser welding and other knownmethods. In some embodiments of the present invention, the canister issealed using a process described in U.S. Pat. No. 7,575,425 to Hall etal. After the canister 2601 is sealed, it is placed within a salt form(not shown). One or more salt forms are then stacked and placed on ananvil of a high-temperature, high-pressure press (not shown). The pressapplies a pressure and a temperature sufficiently high to cause theunsintered abrasive material 2620 (and any catalysts and othermaterials) to sinter. During the sintering process, the abrasivematerial 2620 typically reduces in volume as it becomes solid. Inaddition, the PCD segments 2610 undergo a second, or double, sinteringprocess, by which the PCD grains grow and/or other non-metalliccatalysts and/or other thermally stable materials are incorporated andsintered into the PCD segments as discussed above.

During the sintering process, the abrasive material 2620 forms both amechanical and a chemical bond or attachment with the PCD segments 2610at the interfacial boundary 2650 and at a lower surface 2611. Forexample, the PCD segments 2610 would exhibit, in part, growth of PCDgrains 201 (FIG. 2) into the interstices and voids 220 (FIG. 2) acrossand into a transition zone 2621 of the now sintered abrasive material2620. In so doing, a solid, rigid diamond layer at the transition zone2621 forms a mechanical bond between the sintered layer of abrasivematerial 2620 and the PCD segments 2610, reducing any residual stressconcentrations that may otherwise occur. Further, the abrasive material2620 may reduce in volume as it sinters, provided further space intowhich PCD grains may grow during the sintering process, furtherimproving the mechanical bond. It should be noted that while the grainsize of the PCD grains and the sintered abrasive material can varysubstantially, a grain size that is similar between the PCD grains andthe sintered abrasive material can improve and provide a more uniformbond between the two materials as compared to the bond that occurs whenthe grain sizes are dissimilar.

Another benefit is that whereas the PCD segments 2610—typicallyprocessed to be thermally stable—and the substrate 2625 typically havecoefficients of thermal expansion that are quite different, as discussedabove, the layer of sintered abrasive material 2620 acts as a transitionlayer, and is typically selected and prepared to have a coefficient ofthermal expansion somewhere between that of the PCD segments 2610 andthe substrate 2625. In so doing, the gradient of thermal stresses ischanged gradually throughout the PCD compact rather than having a sharptransition at each interface. That is, a first layer of PCD segments2610 is configured to remain thermally stable at a first temperature anda second layer or transition layer 2620 is configured to remainthermally stable at a second temperature lower than the firsttemperature.

Disclosed in FIGS. 7-14 are various, non-limiting embodiments of PCDcompacts comprising PCD segments of various shapes and the interfacialboundaries between each PCD segment.

For example, the PCD compact 710 includes two PCD segments 710 and asingle interfacial boundary 750 that is non-linear and non-planar andincludes interlocking features 760, such as the illustrated dimples.

As illustrated in FIGS. 7-14, the PCD segments 710, 810, 910, 1010,1110, 1210, 1310, and 1410 can be a variety of shapes, including, butnot limited to, circular, square, hexagonal or a polygonal workingsurface. The PCD segments 710, 810, 910, 1010, 1110, 1210, 1310, and1410 can be arranged symmetrically or asymmetrically around the PCDcompacts 701, 801, 901, 1001, 1101, 1201, 1301, and 1401. Further, thePCD segments can be oriented relative to the direction of work so thatthe PCD segments perform the majority of the work as compared to theabrasive material.

As noted, the interfacial boundaries 750, 950, and others can includecomprise interlocking features. The interfacial boundaries 950 includesa series of steps 960. The interlocking features 750, 850, 950, 1050,1150, 1250, 1350, and 1450 optionally include also comprisecomplementary projections and recesses. For example, PCD compact 1201 inFIG. 12 includes a PCD segment 1210 that has a interfacial boundary 1250that is a plurality of oval openings.

Disclosed in FIGS. 15-20 are cross-sections of various, non-limitingembodiments of PCD compacts 1501, 1601, 1701, 1801, 1901, and 2001. Eachof the PCD compacts 1501, 1601, 1701, 1801, 1901, and 2001 include aplurality of PCD segments 1510, 1610, 1710, 1810, 1910, and 2010,respectively, with an interfacial boundary 1550, 1650, 1750, 1850, 1950,and 2050 separating them, respectively. The transition layers 1515,1615, 1715, 1815, 1925, and 2015 are bonded at lower surface 1511, 1611,1711, 1811, 1911, and 2011 to the PCD segments 1510, 1610, 1710, 1810,1910, and 2010. Likewise, the transition layers 1515, 1615, 1715, 1815,1925, and 2015 are bonded at upper surfaces 1524, 1624, 1724, 1824, 1924and 2024 to the substrates 1525, 1625, 1725, 1825, 1925, and 2025,respectively. The lower surfaces 1511, 1611, 1711, 1811, 1911, and 2011and the upper surfaces 1524, 1624, 1724, 1824, 1924 and 2024 optionallyare non-linear and/or non-planar and/or include interlocking features,such as protrusions and steps.

FIG. 21 shows an embodiment of a drag bit 2800 that includes a pluralityof PCD compacts or shear cutters 2801 as described above. The shearcutters 2801 are attached to blades 2880 that each extend from a head2890 of the drag bit 2800 for cutting against the subterranean formationbeing drilled.

FIG. 22 discloses an embodiment of a PCD compact or pointed cuttingelement 3101 that includes PCD segments 3110 arranged about the PCDcompact or cutting element 3101. The PCD segments 3110 can be arrangedsymmetrically or asymmetrically about the PCD compact 3101 as requiredfor a particular application. A sintered abrasive material 3120 having aconical surface 3123 supports the PCD segments 3110 that, in turn, issupported by a substrate 3125.

FIG. 23 shows an embodiment of another drag bit 3100 that includes aplurality of pointed PCD compacts or cutting elements 3101. The PCDcompacts 3101 may be pressed or machined into the desired shape orconfiguration. In other embodiments, the PCD compact 3101 may be used inroad milling, pavement resurfacing, mining, and trenching applications.

Disclosed in FIGS. 24-26 are various, non-limiting embodiments ofarrangements of the PCD segments 2410, 2510, and 2710 around conical orpointed PCD compacts 2401, 2501, and 2701, that are analogous to the PCDsegments 3110 and the conical PCD compacts 3101 in FIGS. 22 and 23. ThePCD segments 2410, 2510, and 2710 can be of various shapes and sizes,non-limiting examples of which include, but are not limited to,rectangular, trapezoidal, square, hexagonal or triangular shape anddisposed within or exposed in the conical surface, such as conicalsurface 3123 in FIG. 22, as noted. The interfacial boundaries 2450,2550, and 2750 can be formed of a sintered abrasive material.

Whereas the present invention has been described in particular relationto the drawings attached hereto, it should be understood that other andfurther modifications apart from those shown or suggested herein, may bemade within the scope and spirit of the present invention.

The present invention, in various embodiments, includes providingdevices and processes in the absence of items not depicted and/ordescribed herein or in various embodiments hereof, including in theabsence of such items as may have been used in previous devices orprocesses, e.g., for improving performance, achieving ease and/orreducing cost of implementation.

The foregoing discussion of the invention has been presented forpurposes of illustration and description. The foregoing is not intendedto limit the invention to the form or forms disclosed herein. In theforegoing Detailed Description for example, various features of theinvention are grouped together in one or more embodiments for thepurpose of streamlining the disclosure. This method of disclosure is notto be interpreted as reflecting an intention that the claimed inventionrequires more features than are expressly recited in each claim. Rather,as the following claims reflect, inventive aspects lie in less than allfeatures of a single foregoing disclosed embodiment. Thus, the followingclaims are hereby incorporated into this Detailed Description, with eachclaim standing on its own as a separate preferred embodiment of theinvention.

Moreover, though the description of the invention has includeddescription of one or more embodiments and certain variations andmodifications, other variations and modifications are within the scopeof the invention, e.g., as may be within the skill and knowledge ofthose in the art, after understanding the present disclosure. It isintended to obtain rights which include alternative embodiments to theextent permitted, including alternate, interchangeable and/or equivalentstructures, functions, ranges or steps to those claimed, whether or notsuch alternate, interchangeable and/or equivalent structures, functions,ranges or steps are disclosed herein, and without intending to publiclydedicate any patentable subject matter.

1. A polycrystalline diamond compact comprising: a first layer, said first layer including a plurality of polycrystalline diamond segments positioned thereupon; said plurality of polycrystalline diamond segments being separated by an interfacial boundary formed of an abrasive material; a second layer, said first layer being bonded to a second layer, said second layer being formed in part from said abrasive material; and, a substrate, said second layer being positioned upon and bonded to said substrate.
 2. The compact of claim 1, wherein said polycrystalline diamond segments have a granular structure comprised of polycrystalline diamond grains and interstices, said interstices being substantially free of a catalytic material.
 3. The compact of claim 2, wherein said interstices include a non-catalytic material.
 4. The compact of claim 3, wherein said non-catalytic material is a non-metallic material.
 5. The compact of claim 1, wherein said polycrystalline diamond segments have a granular structure comprised substantially of polycrystalline diamond grains and substantially free of interstices.
 6. The compact of claim 1, wherein said abrasive material comprises a granular structure comprised of polycrystalline diamond grains and a catalyst.
 7. The compact of claim 1, wherein the second layer further comprises a substantially conical surface.
 8. The compact of claim 1, wherein said first layer is configured to remain thermally stable at a first temperature and said second layer is configured to remain thermally stable at a second temperature lower than said first temperature.
 9. A polycrystalline diamond compact comprising: a plurality of double-sintered polycrystalline diamond segments, said diamond segments configured to remain thermally stable at a first temperature; a transition layer of single-sintered polycrystalline diamond configured to remain thermally stable at a second temperature lower than said first temperature, said polycrystalline diamond segments positioned upon and bonded to said transition layer; and, a substrate, said transition layer positioned upon and bonded to said substrate.
 10. The compact of claim 9, wherein said polycrystalline diamond segments have a granular structure comprised of polycrystalline diamond grains and interstices, said interstices being substantially free of a catalytic material.
 11. The compact of claim 10, wherein said interstices include a non-catalytic material.
 12. The compact of claim 11, wherein said non-catalytic material is a non-metallic material.
 13. The compact of claim 9, wherein said polycrystalline diamond segments have a granular structure comprised substantially of polycrystalline diamond grains and substantially free of interstices.
 14. The compact of claim 9, wherein said transition layer comprises a granular structure comprised of polycrystalline diamond grains and a catalyst.
 15. The compact of claim 9, wherein the transition layer further comprises a substantially conical surface.
 16. A method of forming a polycrystalline diamond compact comprising: providing a canister configured to receive a plurality of sintered polycrystalline diamond segments and an unsintered abrasive powder; filling said canister with said unsintered abrasive powder; positioning said plurality of polycrystalline diamond segments upon said unsintered abrasive powder, an interfacial boundary formed of said unsintered abrasive powder separating each of said plurality of polycrystalline diamond segments; and applying a temperature and a pressure to said canister to sinter said unsintered abrasive powder and bond said polycrystalline diamond segments to said sintered abrasive powder.
 17. The method of claim 16, further comprising positioning a substrate in said canister, said unsintered abrasive powder being positioned between said substrate and said sintered polycrystalline diamond segments.
 18. The method of claim 16, further comprising: providing another canister configured to receive at least a first disc, said first disc including at least one rib on a front surface of said first disc; filling said canister with at least diamond powder; placing said first disc in said canister such that said front surface of said first disc is in contact with said diamond powder; and, applying a temperature and a pressure to said canister to sinter said diamond powder to form said sintered polycrystalline diamond segments.
 19. The method of claim 18, further comprising: removing said sintered polycrystalline diamond segments from said another canister; processing said polycrystalline diamond segments to make said polycrystalline diamond segments more thermally stable than unprocessed polycrystalline diamond segments. 